Cylinder apparatus with a capability of detecting piston position in a cylinder

ABSTRACT

A cylinder apparatus with a capability of detecting a piston position includes a cylinder, a throttling valve, a positive limit and a pressure switch. A piston is movably mounted in the cylinder. A piston rod with an outside end protruding out of the cylinder is attached to the piston and adapted to push an object. The cylinder is connected to a pump with pipes. The throttling valve and the pressure switch are connected to the pipes, and the pressure switch is installed between the cylinder and the throttling valve. Consequently, when the pump starts pumping, the piston rod pushes the object to abut the positive limit. The stopped movement of the piston rod will change the pressure in the cylinder that triggers the pressure switch to send a signal to a controlling host to stop the pump.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a cylinder apparatus, and moreparticularly to a hydraulic or pneumatic system cylinder apparatus witha capability of detecting a piston position in a cylinder of thecylinder apparatus.

2. Description of Related Art

In most hydraulic and pneumatic powered devices, cylinder apparatusesare the basic actuating elements. With reference to FIG. 4, aconventional cylinder apparatus with a capability of detecting a pistonposition includes a cylinder (50), reed switches (54) and permanentmagnets (521). The cylinder (50) generally includes a closed tubularhousing (51), a piston (52) and a piston rod (53). Since operation ofthe cylinder (50) is conventional, no description of the cylinder (50)operation is provided.

The conventional method of detecting the piston (52) position in acylinder (50) uses the permanent magnets (521) and reed switches (54).The permanent magnet (521) is ring shaped and mounted around the piston(52). The reed switches (54) are respectively strapped to specificpositions on the closed tubular housing (51). When the piston (52) movestoward top dead center or bottom dead center in the closed tubularhousing (51) and passes a reed switch (54), the magnetic field of thepermanent magnet (521) will trigger the reed switch (54). The reedswitch (54) will send an electric signal to a host (not shown) thatcontrols the entire system and stops or starts the piston moving anddetermines the direction of movement.

However, the conventional cylinder apparatus with a capability ofdetecting the piston position in the cylinder (50) still has thefollowing shortcomings.

1. Inconvenient Operation:

Because the reed switch (54) is strapped or clamped on the closedtubular housing (51), the reed switches (54) must be repeatedlyunclamped and clamped to change or adjust the piston (52) position inthe cylinder (50) to push an object to a required position. Especially,when the cylinder (50) is mounted inside a complex machine, unclampingor clamping the reed switches (54) is not easy and is inconvenient.

2. Limited Application:

As described in the foregoing description, the reed switches (54) sensethe magnetic field induced by the permanent magnets (521) and send outan electric signal to the host. However, if the conventional cylinderapparatus is used in a machine that has a strong magnetic field aroundor in the machine, the reed switches (54) will sense the strong magneticfield and lose its capability to sense the position of the piston (52)correctly. Therefore, applications of the cylinder apparatus aresignificantly diminished and can only be used in machines that do nothave strong magnetic fields. To overcome the shortcomings, the presentinvention provides a cylinder apparatus with a capability of detecting apiston position in a cylinder of the cylinder apparatus to mitigate orobviate the aforementioned problems.

SUMMARY OF THE INVENTION

The main objective of the invention is to provide a cylinder apparatuswith a capability of detecting a piston position that is convenient touse.

Another objective of the invention is to provide a cylinder apparatusthat can be broadly used in any hydraulic and pneumatic device.

Other objectives, advantages and novel features of the invention willbecome more apparent from the following detailed description when takenin conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of a cylinder apparatus in accordance with thepresent invention used in a simple hydraulic system;

FIG. 2 is a schematic diagram of the cylinder apparatus in FIG. 1 usedin a simple hydraulic system;

FIG. 3 is a schematic diagram of an alternative embodiment of thecylinder apparatus used in a simple hydraulic system; and

FIG. 4 is a side plan view of a conventional cylinder apparatus with acapability of detecting piston position in a cylinder.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT

With reference to FIGS. 1 and 2, a cylinder apparatus with a capabilityof detecting piston position comprises a cylinder (10), pressureswitches (20), throttling valves (30, 30′) and a positive limit (40).The cylinder apparatus can be used in a hydraulic system or a pneumaticsystem. A double-acting cylinder with a piston rod used in a hydraulicsystem is described, but a person skilled in the art will recognize thata single-acting cylinder or a double-acting cylinder with two oppositepiston rods can be used.

The cylinder (10) is connected to a pumping device (not numbered) of thehydraulic system. The pumping device has a pump (60), pipes (notnumbered) and directional control valves (61). The pump (60) iselectrically connected to a controlling host (not shown) and pumpshydraulic fluid into the cylinder (10) via the pipes.

The cylinder (10) includes a closed tubular housing (11), a piston (12)and an actuating device (not numbered). A complex hydraulic system canbe constructed with the pump (60), the directional control valves (61)and the pipes, and a sophisticated cylinder (10) can also be constructedwith the closed tubular housing (11), the piston (12) and the actuatingdevice. A chamber (not number) is defined in the closed tubular housing(11), and the piston (12) is movably mounted in the chamber to movereciprocally in the closed tubular housing (11) and splits the chamberinto a protruding chamber (111) and a retracting chamber (112). Theactuating device is attached to the piston (12) and is adapted to pushor carry an object to a proper position, where a next process will dealwith the object. The actuating device in this preferred embodiment is apiston rod (13) with an inside end (not numbered) and an outside end(not numbered). The actuating device could be a carrier (not shown)attached to the piston (12) to carry the object for rodless cylinders,such as magnetic rodless cylinders. The inside end of the piston rod(13) is attached to the piston (12) in the closed tubular housing (11).The outside end of the piston rod (13) protrudes out of the closedtubular housing (11) and is adapted to push the object, such as a bottle(41) to a proper position.

The protruding and the retracting chambers (111, 112) are respectivelyconnected to the pump (60) by means of the pipes through a directionalcontrol valve (61). The directional control valve (61) is connected tothe pipes between the pump (60) and the cylinder (10) and is used tochange the path of the hydraulic fluid pumped out of the pump (60) intothe two chambers (111, 112). A throttling valve (30′) is connected tothe pipes between the directional control valve (61) and the protrudingchamber (111) in the closed tubular housing (11) and is used to controlthe flow rate of the hydraulic fluid flowing into or out of theprotruding chamber (111). Therefore, the piston rod (13) can smoothlymove out of the closed tubular housing (11) or smoothly retract into theclosed tubular housing (11) by changing the path and the flow rate ofthe hydraulic fluid into the different chambers (111, 112). Aone-direction throttling valve (30) is connected to the pipes betweenthe directional control valve (61) and the retracting chamber (112) inthe closed tubular housing (11) and throttles the flow rate of thehydraulic fluid flowing out of the retracting chamber (112). Thepressure switch (20) is connected to the pipes between the one-directionthrottling valve (30) and the retracting chamber (112) and can betriggered by a pressure change in the retracting chamber (112). Thepressure switch (20) can convert a physical signal to an electricalsignal and send the electrical signal to the controlling host thatcontrols the pump (60) and the directional control valve (61) to changethe path of the hydraulic fluid.

The positive limit (40) is positioned corresponding to the outside endof the piston rod (13) with a given distance that represents the properposition of the bottle (41) being moved. The bottle (41) is pushed bythe outside end of the piston rod (13) to move until the bottle (41)abuts against the positive limit (40).

To operate the cylinder apparatus, only an appropriate pressure switch(20) has to be installed. When the hydraulic fluid flows into theprotruding chamber (111) by the pump (60) continuously pumping, thepressure in the protruding chamber (111) will be instantly increased.However, the pressure in both the protruding chamber (111) and theretracting chamber (112) will be equalized. Therefore, a forceproportional to the pressure in the protruding chamber (111) is producedand pushes the piston (12) toward the retracting chamber (112) toequalize the pressure in both chambers (111, 112). At the same time, thehydraulic fluid in the retracting chamber (111) flows out and the flowrate of the hydraulic fluid is controlled by the one-directionthrottling valve (30) such that the piston (12) can smoothly move. Thus,the bottle (41) is pushed by the outside end of the piston rod (13) tomove until the bottle (41) abuts the positive limit (40). For aninstant, the pressure in the retracting chamber (112) will be decreasedwhile the movement of the bottle (41) is stopped by the positive limit(40). The decrement of the pressure in the retracting chamber (112) willtrigger the pressure switch (20) to send the electrical signal to thecontrolling host to stop pumping or changing the path of the hydraulicfluid. At this time, the piston rod (13) can be retracted, and thebottle (41) is pushed to the proper position, where a next process in aproduct line is prepared to handle the bottle (41), such as a sealingprocess for the bottle (41).

The pressure in the retracting chamber (112) is generally changed as theoutside end of the piston rod (13) pushes the bottle (41) to abut thepositive limit (40) each time. Therefore, the given distance between thepositive limit (40) and an original position of the outside end of thepiston rod (13) will represent a proper movement of the bottle (41).Consequently, the movement of the piston rod (13) will be equal to thegiven distance between the positive limit (40) and the original positionof the outside end of the piston rod (13). Manufactures only have toadjust the positive limit (40) corresponding to the outside end of thepiston rod (13). The object, such as the bottle (41) will always bepushed to abut the positive limit (40) with the proper position, wherethe sealing process deals with the bottle (41).

With reference to FIG. 3, an alternative embodiment of the invention hasan additional feature that can be implemented with a one-directionthrottling valve (30) and a pressure switch (20) connected to the pipesbetween the protruding chamber (111) and the directional control valve(61). In such a structure, when the outside end of the piston rod (13)pushes the bottle (41) against the positive limit (40), the pressure inthe retracting chamber (112) will decrease and the pressure in theprotruding chamber (111) will increase. Therefore, the controlling hostcan receive two electrical signals that are respectively sent out by thetwo pressure switches (20) that are respectively triggered by thechanges of the pressure in the chambers (111, 112). The controlling hostcan compare with the two signals and take a suitable action to positionthe bottle (40) in an exact position each time. For instance, if thecontrolling host does not receive the signals sent out by both thepressure switches (20) at the same time, one of the pressure switches(20) may be broken down or working abnormally. The controlling hostcould stop the movement of the piston (12) and send out alarms to notifya repairman to check the pressure switches (20) to avoid any possiblemistakes occurring.

The cylinder apparatus is very convenient to adjust. The pressure switch(20) can be installed and connected to the pipes at any conveniently andeasily accessible position to make replacement of the pressure switch(20) convenient and easy. The pressure switches (20) are standardproducts in the hydraulic and pneumatic actuating industry, and a properpressure switch (20) is conveniently selected to install. Also, thecylinder apparatus with a capability of detecting a piston position asdescribed overcomes interference by spurious magnetic fields.

Even though numerous characteristics and advantages of the presentinvention have been set forth in the foregoing description, togetherwith details of the structure and function of the invention, thedisclosure is illustrative only, 11 and changes may be made in detail,especially in matters of shape, size, and arrangement of parts withinthe principles of the invention to the full extent indicated by thebroad general meaning of the terms in which the appended claims areexpressed.

1. A cylinder apparatus with a capability of detecting piston positionin a cylinder of a cylinder and the cylinder apparatus comprising: acylinder having a closed tubular housing with a chamber defined in theclosed tubular housing and adapted to connect to a pump with pipes; apiston movably mounted in the chamber in the closed tubular housing andsplitting the chamber into a retracting chamber and a protrudingchamber; and an actuating device coupled to the piston and adapted toselectively push and carry an object; a positive limit positionedcorresponding to the actuating device adapted to stop movement of theactuating device; a first throttling valve selectively connected to thepipes between one of the retracting and the protruding chambers and thepump; and a first pressure switch connected to the pipes between thefirst throttling valve and the chamber.
 2. The cylinder apparatus asclaimed in claim 1, wherein the actuating device is a piston rod with aninside end and an outside end, the inside end of the piston rod attachedto the piston in the closed tubular housing and the outside end of thepiston rod extending out of the closed tubular housing and adapted topush the object to abut the positive limit.
 3. The cylinder apparatus asclaimed in claim 2, wherein the first throttling valve is connected tothe pipes between the retracting chamber in the closed tubular housingand the pump, and the first pressure switch is connected to the pipesbetween the retracting chamber in the closed tubular housing and thefirst throttling valve.
 4. The cylinder apparatus as claimed in claim 2,wherein the first throttling valve is connected to the pipes between theprotruding chamber in the closed tubular housing and the pump, and thefirst pressure switch is connected to the pipes between the protrudingchamber in the closed tubular housing and the first throttling valve. 5.The cylinder apparatus as claimed in claim 4, wherein the cylinderapparatus further comprises a second throttling valve connected to thepipes between the retracting chamber in the closed tubular housing andthe pump, and a second pressure switch connected to the pipes betweenthe retracting chamber in the closed tubular housing and the secondthrottling valve.
 6. The cylinder apparatus as claimed in claim 3,wherein the first throttling valve is one-directional.
 7. The cylinderapparatus as claimed in claim 4, wherein the first throttling valve isone-directional.
 8. The cylinder apparatus as claimed in claim 5,wherein both the first and the second throttling valves areone-directional.